FIELD OF THE INVENTION
This invention relates to an image processing method and an apparatus therefor. More particularly, the invention relates to an image processing method and apparatus for converting original image data having a "flat" appearance, such as that of a photograph, into aesthetic image data having a pictorial (painter-like) touch.
Mosaic processing is one example of a method employed in the art for creating an aesthetic image by applying image processing technology. This entails executing mosaic processing of an image in which, say, a total of 25 pixels in a 5.times.5 array of pixels in the X and Y directions serves as a block unit. More specifically, letting an item of original image data having an address (x,y) be represented by a(x,y), an item of image data a'(x,y) resulting from mosaic processing is determined by the following equation: EQU a'(5m-i, 5n-j)=a(5m-3, 5n-3) (1)
where
i, j: pixel numbers (1, 2, 3, 4, 5 each) PA1 m, n: block numbers (1, 2, 3, . . . each)
That is, the central item of image data a(5m-3, 5n-3) in each block of the original image data is a representative value. Mosaic conversion processing is performed by replacing all of the items of image data a'(5m-i, 5n-j) that have been subjected to mosaic processing in the relevant block by the abovementioned representative value. It should be noted that the representative value is not limited to the central item of pixel data, for any item of pixel data within the block can serve as a representative value. There are also cases in which the mean value within a block is employed as the representative value.
Applications of mosaic processing to pictorial representation are disclosed in Japanese Patent Application Laid-Open (KOKAI) Nos. 62-179059, 62-179060 and 62-179061. According to these disclosures, the mosaic pattern is generated at random positions by a random function, or the size of a mosaic pattern is varied in dependence upon the contrast or spatial frequency characteristic of the original image data.
However, the conventional mosaic pattern is expressed by binary data of value "0" or "1". For this reason, gradations in coloring materials or pigments, build-up or mounding of the coloring materials and other pictorial touches cannot be expressed. Only a picture having a flat impression can be obtained, and it is impossible to achieve a high-grade image conversion.
In addition, the prior art is such that one type of shape pattern (brush pattern) constituting a mosaic is prepared per image, and a portion of this shape pattern is used by being cut from the pattern in dependence upon the contrast information and spatial frequency information obtained from the original image data. As a consequence, the shape of the brush pattern is destroyed and a real brush-like touch cannot be expressed.
Furthermore, with an apparatus of this type, the prior art requires the provision of separate memory means as a so-called working area for image processsing and the like. However, this necessitates a large memory capacity and is extremely uneconomical.
The assignee of the present invention has already proposed the case indicated below, in which the binary mosaic pattern is varied in dependence upon the edge direction detected;
U.S. application Ser. No. 174,979 (filed Mar. 29, 1988)
However, further improvements are sought.